To meet the demand for natural resources, companies often invest significant amounts of time and money in searching for and extracting oil, natural gas, and other subterranean resources from the earth. Particularly, once a desired resource is discovered below the surface of the earth, drilling and production systems are often employed to access and extract the resource. These systems may be located onshore or offshore depending on the location of a desired resource. Further, such systems generally include a completion system that includes a wellhead assembly through which the resource is extracted. These completion systems may include a wide variety of components, such as various casings, hangers, valves, fluid conduits, and the like, that control drilling and/or extraction operations.
One type of completion assembly includes a wellhead with one or more strings of casing supported by casing hangers in the wellhead. Attached to the wellhead is a tubing spool. A tubing hanger secured to a string of tubing lands in the tubing spool above the wellhead or directly in the wellhead. The tubing hanger has a plurality of passages that provide access through the tubing hanger for hydraulic fluid or electrical lines to operate and control equipment located downhole, such as safety valves, temperature sensors, or chemical injection units, for instance.
A tree (sometimes referred to in the oil and gas industry as a christmas tree) may be installed on top of the tubing spool. The tree typically has a bore in fluid communication with the tubing string and tubing hanger and valves for controlling flow through the well. The passages in the tubing hanger connect with passages in the tree, which may provide access to a control unit in the tree.